Rotor of electric rotating machine

ABSTRACT

Deformation and vibration of claw magnetic poles in rotor are reduced. A rotor includes: a rotor coil  15  for generating a magnetic flux by applying a current; a pole core comprised of a first pole core body  19  and a second pole core body  20  that are disposed so as to cover the rotor coil  15 , each being provided with claw-shaped claw magnetic poles  21, 22  engaging with each other; and a magnet assembly  25  composed of a magnet  23  for reducing leakage of magnetic flux and a magnet-holding member  24  for supporting the magnet  23  on the claw magnetic poles  21, 22 . Center of gravity  25 G of the magnet assembly  25  is located on the base part side nearer than the center of the claw magnetic poles  21, 22.

This is a divisional application of Ser. No. 10/663,775 filed Sep. 17,2003 now U.S. Pat. No. 7,009,324. The entire disclosure of priorapplication Ser. No. 10/663,775 is considered part of the disclosure ofthe accompanying divisional application and is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotor structure of an electricrotating machine such as an ac generator or an electric motor and, moreparticularly, to a structure of fitting a magnet that prevents leakageof magnetic flux between claw magnetic poles.

2. Description of the Related Art

In a conventional rotor structure, rectangular parallelepiped magnetspolarized in a direction of reducing leakage of magnetic flux betweensides of adjacent claw magnetic poles are fixed between the clawmagnetic poles facing each other, and holders for reducing centrifugalforce are used to fit these magnets.

When the magnets for preventing leakage of magnetic flux are fitted tothe claw magnetic poles of a rotor core as described above, the clawmagnetic poles increase in weight. Therefore, end of each claw magneticpole reciprocates toward a rotor coil and a stator due to centrifugalforce caused by rotation of the rotor and magnetic attraction betweenthe claw magnetic pole and the stator produced at the time of powergeneration.

As a result, a load is applied to the magnets between the claw poles,and this sometimes may cause distortion or breakage of the magnets.

To overcome this, in a conventional rotor, a magnet is fixed to eachclaw magnetic pole in such a manner as to cover an inner circumferentialface and a side face of the claw magnetic pole.

In this known construction, spaces are left between the adjacentmagnets.

As a result, the claw magnetic poles and the magnets reciprocateindependently; therefore, no load is applied to the magnets, and it ispossible to prevent the magnets from breakage (for example, see JapanesePatent Publication (unexamined) No. 1999/136913, pages 3 and 4).

In another conventional rotor, each claw magnetic pole is provided withtwo ferrite magnets on both side faces of each claw pole, and thesemagnets are polarized so as to reduce leakage of magnetic flux betweenthe claw magnetic poles.

These magnets are supported on the claw magnetic poles, with a slant soas to spread their outer circumference sides toward each other, bymagnet-holding members for absorbing centrifugal force that acts on thementioned magnets when the rotor is rotating through deformation of themagnet-holding members themselves. Thus, the magnets are so constructedas to withstand centrifugal force (for example, see Japanese PatentPublication (unexamined) No. 2001/86715, page 6).

The permanent magnets are fitted to the claw magnetic poles for thepurpose of reducing leakage of magnetic flux between the side faces ofthe adjacent claw magnetic poles and leakage of magnetic flux from theirinside diameter faces, thereby improving output of the electric rotatingmachine.

However, fitting the magnets brings about a contrary effect, i.e., theclaw magnetic pole as a whole increases in weight and the claw magneticpole receives more centrifugal force caused by rotation of the rotor.

In particular, increase in weight of the end portion of the clawmagnetic pole invites increase in deformation spreading toward a stator.

Hence, it is necessary to enlarge an air gap between the rotor and thestator in order to prevent breakage.

However, this air gap has a close relationship to the output, i.e., themore the air gap is decreased, the more output is increased.

Therefore, it is necessary that the magnets be fixed so as to restraindeformation of the claw magnetic poles from the viewpoint of furtherimproving the output.

In the meanwhile, the magnet-holding members for fitting the magnets tothe claw magnetic poles are influenced by the deformation of the clawmagnetic poles and change in number of rotation of the rotor, and thereis a possibility that the magnet-holding members or the magnetsthemselves are broken or get out of position due to vibration of theclaw magnetic poles.

Moreover, the known structure of fitting the magnets to the clawmagnetic poles also has a problem that it is not possible to efficientlyassemble the rotor because interference in magnetic position occursbetween the pole cores at the time of assembling the rotor.

SUMMARY OF THE INVENTION

The present invention was made to solve the above-discussed problems andhas an object of providing a rotor structure in which fitting structureof the magnets for preventing leakage of magnetic flux between the clawmagnetic poles is designed so as to reduce centrifugal force caused byrotation of the rotor, reduce deformation and vibration of the clawmagnetic poles, thus improving efficiency in assembling the rotor.

A rotor of an electric rotating machine according to the presentinvention includes: a rotor coil for generating a magnetic flux byapplying a current, and a pole core comprised of a first pole core bodyand a second pole core body that are disposed so as to cover the rotorcoil, each being provided with claw-shaped claw magnetic poles engagingwith each other. In the rotor, a magnet assembly composed of a magnetfor reducing leakage of magnetic flux and a magnet-holding member forsupporting this magnet on the claw magnetic poles is arranged on theclaw magnetic poles. Each magnet assembly is arranged so that a centerof gravity thereof is located on the base part side at the portionnearer than the center of said magnetic claw poles.

As a result, deformation of the claw magnetic poles is reduced, andchange in position due to vibration is also reduced and, therefore, itis possible to prevent the magnet-holding members from breaking andprevent the magnet assembly from getting out, and the air gap betweenthe rotor and the stator can be reduced. Consequently, it is possible toimprove the output.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side view showing an electric rotating machineaccording to Embodiment 1 of the present invention.

FIG. 2 is a perspective view showing a rotor portion according toEmbodiment 1 of the invention.

FIG. 3 is a perspective view showing a rotor portion according toEmbodiment 2 of the invention.

FIG. 4 is a perspective view showing a rotor portion according toEmbodiment 3 of the invention.

FIG. 5 is a perspective view showing a claw magnetic pole portion.

FIG. 6 is a perspective view showing a rotor portion according toEmbodiment 4 of the invention.

FIG. 7 is a perspective view showing a claw magnetic pole portion.

FIG. 8 is a perspective view showing a claw magnetic pole portion.

FIG. 9 is a perspective view showing a claw magnetic pole portion.

FIG. 10 is a sectional side view showing a claw magnetic pole portion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

FIG. 1 is a sectional side view showing an electric rotating machine inits entirety such as an ac generator or an electric motor according toone embodiment of the present invention. Referring to the drawing, thiselectric rotating machine is provided with a housing 3 comprised of afront bracket 1 and a rear bracket 2 both made of aluminum, a shaft 6disposed in this housing 3 and provided with a pulley 4 fixed onto anend thereof, a Randell-type rotor 7 fixed onto this shaft 6, fans 5fixed onto both end faces of this rotor 7, a stator 8 fixed onto aninner wall face in the housing 3, a slip ring 9 that is fixed to theother end of the shaft 6 and supplies the rotor 7 with a current, a pairof brushes 10 sliding on this slip ring 9, a brush holder 11 in whichthese brushes 10 are accommodated, a rectifier 12 that is electricallyconnected to the stator 8 and rectifies an alternating current generatedin the stator 8 into a direct current, a heat sink 13 fitted to thebrush holder 11, and a regulator 14 adhering to this heat sink 13 andregulating the alternating voltage generated in the stator 8.

The rotor 7 is provided with a cylindrical rotor coil 15 for generatinga magnetic flux by applying an electric current and a pole core 16constructed so as to cover this rotor coil 15. Magnetic flux generatedby the rotor coil 15 forms a magnetic pole in the pole core 16.

The stator 8 is provided with a stator core 17 and a stator coil 18wound around this stator core 17, in which alternating current isgenerated by a change in magnetic flux from the rotor coil 15 withrotation of the rotor 7.

The pole core 16 is comprised of a first pole core body 19 and a secondpole core body 20 engaging with each other and forming a pair.

The first pole core body 19 and the second pole core body 20 arenormally composed of iron, each being comprised of a cylindrical part 19a, 20 a around which the rotor coil 15 is wound and a disk-shaped basepart 19 b, 20 b from which the cylindrical part 19 a, 20 a protrudes.

The outer edges of the base parts 19 b, 20 b are provided with pluralclaw magnetic poles 21, 22 engaging with each other between the outercircumference of the rotor coil 15 and the inner circumference of thestator 8, respectively.

Each claw magnetic pole 21, 22 is formed so as to be thick and wide onthe base part 19 b, 20 b side while gradually decreasing in thicknessand width (tapered) toward the end side.

An inner circumferential face of each claw magnetic pole 21, 22gradually decreases in thickness toward the end thereof while an outercircumferential face being arc-shaped extends along the innercircumferential face of the stator 8.

Each of claw magnetic poles 21, 22 has two trapezoidal side faces withrespect to the circumferential direction of the rotor 7.

The claw magnetic poles 21 and 22 are engaged with each other with theirends opposite to each other and, therefore, slants of the innercircumferential faces of the claw poles 21, 22 are alternately arrangedin the circumferential direction.

Side faces of the claw magnetic poles 21, 22 gradually decrease in widthfrom the base side to the end side and incline toward the center of theclaw poles 21, 22.

Now, operation of the rotor is hereinafter described.

A battery (not shown in the drawings) supplies an electric current tothe rotor coil 15 through the brushes 10 and the slip ring 9 so as togenerate a magnetic flux. Thus, the claw magnetic poles 21 of the firstpole core body 19 are polarized with the N-pole, and the claw magneticpoles 22 of the second pole core body 20 are polarized with the S-pole.

On the other hand, the rotating force of engine drives the pulley 4, theshaft 6 rotates the rotor 7 and, as a result, an electromotive force isgenerated in the stator coil 18.

This alternating electromotive force is rectified into a direct currentthrough the rectifier 12 and the regulator 14 regulates intensitythereof, whereby the battery is charged with the direct current.

On the other hand, it is possible to use the rotor as a motor byapplying a voltage to the respective ac terminals.

FIG. 2 is a partial perspective view showing a rotor portion. In thedrawing, each claw magnetic pole 21 is provided with two neodymiummagnets 23, which are polarized so as to reduce leakage of magnetic fluxbetween the magnetic claw magnetic poles 21 and 22, on both sides ofeach claw magnetic pole 21, and each claw magnetic pole 22 is providedwith two neodymium magnets 23 on both sides of each claw magnetic pole22.

These two magnets 23 are supported on the claw magnetic poles 21, 22 bymagnet-holding members 24, and the magnets 23 and the magnet-holdingmembers 24 form a magnet assembly 25.

The mentioned magnet-holding members 24 are respectively formed bybending a stainless steel (SUS304) plate of 0.5 mm in thickness, and aremanufactured with ease.

Each magnet assembly 25 is trapezoidal plate-shaped so as to graduallyincrease in thickness toward the base side in the circumferentialdirection, and the magnet assembly 25 is so arranged that center ofgravity 25G thereof is located on the base part side at the portionnearer than the center of the claw magnetic poles 21, 22.

Further, a face of the magnet assembly 25 being in contact with the clawmagnetic poles 21, 22 is also trapezoidal plate-shaped extending alongthe magnetic pole.

The magnet assembly 25 is fixed to the claw poles 21, 22 with anadhesive or the like.

Specifically, an adhesive or the like is applied between the innercircumferential face of the claw magnetic poles 21, 22 and the innercircumferential part of the magnet-holding member 24.

The claw magnetic poles 21, 22 and the magnet-holding member 24 are bothmade of metal and, therefore, it is also preferable to fix themagnet-holding member 24 to the claw poles 21, 22 by welding.

By employing the configuration as described above, a center of gravity25G of the magnet assembly 25 is established on the base side of theclaw magnetic poles 21, 22 of high rigidity, whereby the end side of theclaw magnetic poles 21, 22 moving largely is reduced in weight.

When rotating the rotor 7 under the above-mentioned situation, the endpart of the claw magnetic poles 21, 22 moving largely receivescentrifugal force less than in the conventional art, and the base partmoving less comes to receive centrifugal force more.

The claw magnetic pole 21, 22 are cantilevered and supported on the basepart and, therefore, the centrifugal force on the end part is reduced.Thus, it becomes possible to restrain movement of the end part andreduce the air gap between the rotor 7 and the stator 8. As a result,output of the electric rotating machine is improved.

As described above, in the invention, the center of gravity 25G of themagnet assembly 25 is located near the base side of the claw magneticpoles 21, 22, of which rigidity is high and deformation is small and,therefore, it is possible to reduce not only deformation of the clawmagnetic poles 21, 22, but also change due to vibration.

As a result, it is possible to prevent the magnet-holding members 24from breaking and prevent the magnet assembly 25 from getting out.Furthermore, the air gap between the rotor 7 and the stator 8 is reducedand, consequently, it is possible to improve output.

Embodiment 2

In the foregoing Embodiment 1, the magnet assembly is constructed so asto cover the whole side of the claw magnetic poles and, furthermore, thecenter of gravity is located near the base side. In this Embodiment 2,however, not only the center of gravity of the magnet assembly, but alsothe magnet assembly itself is disposed near the base side of the clawmagnetic poles; thus, the whole magnet assembly is located on the baseside.

More particularly, as shown in FIG. 3, the claw magnetic pole 21 isprovided with magnet assembly 25 a only on both sides of the base part19 b, and the claw magnetic pole 22 is provided with magnet assembly 25b only on both sides of the base part 20 b.

By employing the construction as described above, centrifugal force onthe claw magnetic poles 21, 22 increases only on the base side and,therefore, the end of the claw magnetic poles 21, 22 receives lesscentrifugal force and deformation thereof becomes small. The air gapbetween the rotor 7 and the stator 8 is further reduced as compared withthe foregoing Embodiment 1 and, therefore, it is possible to increaseoutput.

In the foregoing Embodiment 1, two magnet assemblies 25 are disposedbetween the adjacent claw magnetic poles 21, 22, and the thickness ofone magnet-holding member 24 is approximately equal to that of the twomagnet assemblies. On the other hand, in this embodiment, only onemagnet assembly is disposed between the claw poles 21, 22, therebyreducing the thickness of the magnet-holding member 24 by half. As aresult, it is possible to make the size of the neodymium magnet 23 largeand effectively overcome the problem of leakage of magnetic flux fromthe side face.

Further, in case of assembling the rotor 7, since only one magnetassembly is disposed between the claw magnetic poles 21, 22 and, unlikethe foregoing Embodiment 1, it is possible to assemble the rotor 7without interference between the adjacent magnet assemblies, andassembling efficiency is improved.

As described above, since the magnet assembly 25 is constructed so thatnot only center of gravity, but also its external shape, is located nearthe base side of the claw magnetic poles 21, 22, the magnet assembly ismounted only on the base side, deformation in the ends of the clawmagnetic poles 21, 22 is further reduced, and the magnets do notinterfere with each other at the time of fitting.

Furthermore, since only one magnet-holding member 24 is disposed betweenthe claw magnetic poles 21, 22, it is possible to make the size of themagnets 23 large and increase output.

Embodiment 3

FIG. 4 is a partial perspective view showing a rotor portion accordingto Embodiment 3 of the invention, and FIG. 5 is a perspective viewshowing a claw magnetic pole portion.

In this embodiment, the magnet-holding members extend to the base sidealong both side faces of the claw magnetic poles 21, 22.

These extending portions are adhered to the claw magnetic poles 21, 22with an adhesive agent or welded thereto.

By employing the construction as described above, the magnet assembliesare fixed more firmly than those of the foregoing Embodiments 1 and 2and, furthermore, rotation of the claw magnetic poles 21, 22 in thecircumferential direction is restrained.

Furthermore, it is possible to arrange the magnets 23 on the extendingportions, thereby further reducing leakage of magnetic flux.

As described above, according to this embodiment, since the magnetassemblies 25 extend to the base parts of the claw magnetic poles 21,22, the claw magnetic poles 21, 22 do not rotate in the circumferentialdirection, and the magnet assemblies 25 are firmly fitted. Further,since the magnets 23 extend in an axial direction, it is possible tofurther prevent leakage of magnetic flux, eventually increasing output.

Embodiment 4

FIG. 6 is a partial perspective view showing a rotor portion accordingto Embodiment 4 of the invention, and FIG. 7 is a perspective viewshowing a claw magnetic pole portion.

In this embodiment, the magnet-holding members 24 extend furthermore ascompared with the foregoing Embodiment 3 up to the base parts 19 b, 20 bof the claw magnetic poles 21, 22 and are bent and fixed.

By employing the construction as described above, the same advantages asEmbodiment 3 are obtained, and it is possible to prevent the magnetassemblies 25 from moving in an axial direction because the fixed facesare located in the axial direction.

Furthermore, since the portions where the magnet assemblies 25 are fixedto the claw magnetic poles 21 and 22 are located on the axial side, itis possible to fit the magnet assemblies 25 to the claw magnetic poles21, 22 through elastic deformation of the magnet-holding members 24,thus improving assembling efficiency.

As described above, according to this embodiment, extending themagnet-holding members 24 of the magnet assemblies 25 up to the backsideof the pole, it is possible to restrain movement of the magnetassemblies 25 in the axial direction, and the magnet assemblies 25 canbe fitted and fixed with ease because the fixing portions are locatedoutside.

Embodiment 5

FIG. 8 is a partial perspective view showing a rotor portion accordingto Embodiment 5 of the invention. In this embodiment, the extendingmagnet-holding members 24 shown in Embodiment 4 extend further, and bothend points “a” of them are joined and fixed by welding. Subsequently,the magnet-holding members 24 are fixed to the claw magnetic poles 21,22 in the same manner as in the foregoing Embodiment 4.

By employing the construction as described above, the magnet-holdingmembers 24 are improved in rigidity.

As described above, since the magnet-holding members 24 are joined andfixed onto the backside of the pole by welding, the magnet-holdingmembers 24 increase in rigidity and are fixed more firmly.

Embodiment 6

FIG. 9 is a partial perspective view showing a rotor portion accordingto Embodiment 6 of the invention, and FIG. 10 is a sectional side viewof the same portion.

In this embodiment, neodymium magnets 23 are added between the rotorcoil 15 and the claw magnetic poles 21, 22 in order to reduce leakage ofmagnetic flux from the inner circumferential faces of the claw magneticpoles 21, 22 (reverse sides of the claw magnetic poles 21, 22).

By employing the construction as described above, output is furtherimproved.

Since the magnets 23 are additionally fitted on the reverse side of theclaw magnetic poles 21, 22, there is no more such problem as gettingaway the magnets 23 due to centrifugal force.

As described above, according to this embodiment, the magnets 23 aredisposed for preventing leakage of magnetic flux between the adjacentclaw magnetic poles 21, 22 of the pole core. Further the magnets 23 areadditionally disposed for preventing leakage of magnetic flux frominside diameter sides of the claw magnetic poles 20 21, 22, and themagnetic assemblies 25 having the magnet-holding members 24 for fixingthese magnets 23 to the claw magnetic poles 21 and 22 are disposed. As aresult, it is possible to reduce leakage of magnetic flux and improveoutput.

The output can be further improved effectively by combining theconstruction of this embodiment with those described in the foregoingEmbodiments 1 to 5.

Although the foregoing Embodiments 1 to 6 disclose a rotor structure inwhich a field coil is incorporated in the rotor and rotates along withthe claw magnetic poles, and a field current 30 is supplied to the fieldcoil through brushes, the invention is also applicable to abrushless-type generator in which a field coil is fixed to a bracket anda rotating field is supplied from an air gap.

1. A rotor of an electric rotating machine comprising: a rotor coil for generating a magnetic flux by applying a current; and a pole core comprised of a first pole core body and a second pole core body that are disposed so as to cover the rotor coil, each being provided with claw-shaped claw magnetic poles engaging with each other; wherein a plurality of magnetic assemblies, each magnet assembly composed of magnets for reducing leakage of magnetic flux and a magnet-holding member for supporting said magnets on said claw magnetic poles, are arranged on solely a base part side of each of said claw magnetic poles respectively, wherein each magnet assembly is arranged on the side walls of the base part side of only one claw magnetic pole.
 2. The rotor of an electric rotating machine according to claim 1, wherein each of said magnet assemblies extends to the base parts of respective claw poles.
 3. The rotor of an electric rotating machine according to claim 1, wherein each said magnet-holding member extends to a backside of its respective pole and is fitted to its respective pole.
 4. The rotor of an electric rotating machine according to claim 1, wherein said magnets for reducing leakage of magnetic flux are arranged on a reverse side of said claw magnetic poles.
 5. The rotor of an electric rotating machine according to claim 1, wherein each said magnetic holding member is welded to its respective pole. 